Chandra leftovers and Shuttle-launch views

I just learned this interesting tidbit of hardware recycling:

One of the numerous things the CAIB report pointed out was the very
poor and patchy quality of ground-0based imagery of the STS-107
launch. Two of the cameras in the best position to see the foam strike
were seriously compromised - one was badly out of focus, and the other
had a cable wrap issue that kept it from tracking the vehicle long
after launch. This was said to be due to their being USAF assets
tasked on a "best-effort" basis, and they couldn't spare the people that
day. So now NASA is making a set of six new tracking cameras in-house:
62-cm aperture, 8-m focal length Cassegrain-style systems with front
windows to keep out the Florida flying goo.

Flashback: when the largest of the nested mirror segments for the Chandra
observatory was fabricated, it was made from a large and thick boule of
Zerodur low-expansion glass. Being a nearly cylindrical section of
a paraboloid (well, one mirror was a paraboloid and one a hyperboloid,
IIRC), they only needed a thin cylidrical shell around the outside, so they
elegantly drilled a connecting bunch of maybe 3-cm holes and popped the inner
boule out. That hunk of glass stayed in storage until lately - and
it was plenty large enough to cut the blanks for the six tracking-camera
primary mirrors out of. NASA could probably have had this done commercially,
but since the Marshall space-optics facility is between major projects
and can do them almost trivially, they've started from the recycled glass
already.

You never know when old parts will come in handy. It's a good thing nobody
in procurement suggested they put the glass up on eBay...


Bill Keel

.

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